Partially erodable systems for treatment of obstructive sleep apnea

ABSTRACT

The invention relates to devices and methods for reforming tissue surrounding the airway of a subject suffering from obstructive sleep apnea so as to open the airway and alleviate the occurrence of apneic events. Devices comprise a combination of resiliently deformable material and bioerodible material. The deformable portion of the device has a preferred shape that corresponds to the desired final shape of the device once placed in an airway. In making a transplant-ready device, however, the deformable portion is placed into a deformed shape and constrained in that shape by the bioerodible material. After implantation, the device gradually assumes the preferred shape as the constraining bioerodible material erodes. As the device gradually reforms toward the preferred shape, it reforms the tissue into the therapeutically desirable configuration. The gradual nature of the shape change generally stabilizes the device in the tissue, and supports tissue reforming into a stable configuration.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No. 13/954,589filed Jul. 30, 2013 which is a continuation of application Ser. No.13/443,839 filed Apr. 10, 2012, now U.S. Pat. No. 8,523,760, which is adivisional of application Ser. No. 11/969,201 filed Jan. 3, 2008, nowU.S. Pat. No. 8,167,787, each of which is herein incorporated byreference in its entirety.

INCORPORATION BY REFERENCE

All publications, patents and patent applications mentioned in thisspecification are herein incorporated by reference to the same extent asif each individual publication, patent or patent application wasspecifically and individually indicated to be incorporated by reference.

FIELD

The invention relates to the field of methods and devices for thetreatment of obstructive sleep apnea, and more particularly to openingthe airway of subjects with symptoms of obstructive sleep apnea.

BACKGROUND

Sleep apnea is defined as the cessation of breathing for ten seconds orlonger during sleep. During normal sleep, the throat muscles relax andthe airway narrows. During the sleep of a subject with obstructive sleepapnea (OSA), the upper airway narrows significantly more than normal,and during an apneic event, undergoes a complete collapse that stopsairflow. In response to a lack of airflow, the subject is awakened atleast to a degree sufficient to reinitiate breathing. Apneic events andthe associated arousals can occur up to hundreds of times per night, andbecome highly disruptive of sleep. Obstructive sleep apnea is commonlybut not exclusively associated with a heavy body type, a consequence ofwhich is a narrowed oropharyngeal airway.

Cyclic oxygen desaturation and fragmented sleeping patterns lead todaytime sleepiness, the hallmark symptom of the disorder. Furtherconsequences of sleep apnea may include chronic headaches anddepression, as well as diminished facilities such as vigilance,concentration, memory, executive function, and physical dexterity.Ultimately, sleep apnea is highly correlated with increased mortalityand life threatening comorbidities. Cardiology complications includehypertension, congestive heart failure, coronary artery disease, cardiacarrhythmias, and atrial fibrillation. OSA is a highly prevalent diseaseconditions in the United States. An estimated 18 million Americanssuffer from OSA to degrees that range from mild to severe, many of whomare undiagnosed, at least in part because the afflicted subjects areoften unaware of their own condition.

Treatment of OSA usually begins with suggested lifestyle changes,including weight loss and attention to sleeping habits (such as sleepposition and pillow position), or the use of oral appliances that can beworn at night, and help position the tongue away from the back of theairway. More aggressive physical interventions include the use ofbreathing assist systems that provide a positive pressure to the airwaythrough a mask that the subject wears, and which is connected to abreathing machine. In some cases, pharmaceutical interventions can behelpful, but they generally are directed toward countering daytimesleepiness, and do not address the root cause. Some surgicalinterventions are available, such as nasal surgeries, tonsillectomyand/or adenoidectomy, reductions in the soft palate or the uvula or thetongue base, or advancing the tongue base by an attachment to themandible and pulling the base forward. These surgical approaches can bequite invasive and thus have a last-resort aspect to them, and further,simply do not reliably alleviate or cure the condition. There is a needfor less invasive procedures that show promise for greater therapeuticreliability.

SUMMARY

The invention relates to a method of alleviating obstructive collapse ofairway-forming tissues, and for devices with which to implement themethod. Typical patients for whom the method and device may providetherapeutic benefit are those who suffer from obstructive sleep apnea.The method includes implanting a device at a site in the tissue andbioeroding the bioerodible portion of the device to change the shape ofthe device and to remodel the airway-forming tissue. The implanteddevice is sized and shaped to conform to the airway-forming tissue sitein a manner compatible with normal physiological function of the site;and includes a resiliently deformable portion and a bioerodible portion.In typical embodiments of the method, remodeling the airway-formingtissue results in the airway being unobstructed during sleep, andfurther, typically, the thus-unobstructed airway diminishes thefrequency of apneic events. Remodeling may include reshaping orotherwise altering the position or conformation of airway associatedtissue so that its tendency to collapse during sleep is diminished.

The airway is formed from various tissues along its length from themouth to the lungs. Embodiments of the method include implanting apartially-erodible device into any one or more of these tissues,including, for example, the soft palate, the tongue, generally the baseof the tongue, and the pharyngeal walls, typically the posterior andlateral portions of the pharyngeal wall.

In some embodiments, the device is in a deformed shape when implanted,and bioeroding to change the shape of the device includes the shapechanging toward a preferred shape. In some embodiments, the bioerodibleportion of the device constrains the device in a deformed shape prior tothe bioeroding step.

With regard to the bioeroding of the bioerodible portion of the device,this may occur over a time span that ranges from days to months. In someembodiments, the bioeroding proceeds at a rate that correlates with theratio of the biologically-exposed surface area of the bioerodibleportion to the volume of the bioerodible portion.

In some embodiments of the method, the bioerosion occurs at a rate thatis sufficiently slow for the tissue site to recover from the implantingprior to the device substantially changing shape. In some of theseembodiments, the recovery of the tissue site includes a forming offibrotic tissue around the device, which typically stabilizes the devicein the site, and provides the device greater leverage with which toreform the shape of the implant site and its surrounding tissue. In someembodiments, after implanting, and as part of the healing response orrecovery from the implantation wound, the newly formed fibrotic tissuesinfiltrates into holes, pores, or interstices in the device. In someembodiments of the method, a bioactive agent, previously incorporatedinto the bioerodible material, is released or eluted from thebioerodible portion of the device as it is eroding.

In another aspect of the methods described herein, a method of forming adevice to alleviate obstructive collapse of an airway during sleep isprovided. The method includes forming a resiliently deformable materialinto an initial shape that corresponds to the preferred shape of thedevice, the initial shape having a site for accommodating bioerodiblematerial; changing the initial shape of the resiliently deformablematerial into a non-preferred shape that is sized and configured into animplantable shape that conforms to an airway-forming tissue site and iscompatible with normal physiological function after implantation; andstabilizing the implantable shape by incorporating the bioerodiblematerial into the accommodating site. In some of these methodembodiments, changing the initial shape of the resiliently deformablematerial includes absorbing a force sufficient to remodel the airway asthe force is transferred from the device into an implant site afterimplantation of the device. That level of force is further typicallyinsufficient to remodel the airway to an extent that it is unable tomove in a manner that allows substantially normal or acceptablephysiological function of the airway.

As noted above, the invention further provides a device for alleviatingobstruction in an airway, such obstruction typically occurring duringsleep. Embodiments of the device include an implantable device sized andshaped to conform to an airway-forming tissue site in a mannercompatible with normal physiological function of the site, the deviceincluding a resiliently deformable portion and a bioerodible portion. Inthese embodiments, the resiliently deformable portion has a preferredshape that is constrained in a deformed shape by the bioerodibleportion, and the device is configured to return toward the preferredshape of the resiliently deformable portion upon erosion of thebioerodible portion. In some embodiments, the preferred configuration isadapted to remodel the shape of the airway so as to provide a more openairway during sleep.

In typical embodiments of the device, the resiliently deformable portionmay include any one or more of a metal or a polymer. In theseembodiments, a resiliently deformable metal may include any one or moreof stainless steel, spring steel, or superelastic nickel-titanium alloy,and a resiliently deformable polymer may include any one or more ofsilicone rubber, polyesters, polyurethanes, or polyolefins. In someembodiments, the bioerodible portion may include any one or more ofpolycaprolactone, polylactic acid, polyglycolic acid, polylactidecoglycolide, polyglactin, poly-L-lactide, polyhydroxalkanoates, starch,cellulose, chitosan, or structural protein.

Some embodiments of the device include a portion adapted to engage thetissue into which it is implanted, and in some of these embodiments, theso-adapted portion includes a site for tissue in-growth, such in-growthserving to keep the device and tissue in close proximity, serving topromote implant site remodeling in a manner that conforms to thechanging shape of the device. Finally, in some embodiments, theimplantable device is configured with sufficient elasticity to allownormal physiological movement around an airway-forming tissue implantsite when the device is implanted in the implant site.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 provides an overview of the healthy human airway anatomy, withparticular attention to the nasopharyngeal, oropharangeal, andhypopharyngeal regions.

FIG. 2 provides a view of a compromised airway, with an occlusion in theoropharyngeal region due to posterior slippage of the base of the tongueand a thickened posterior pharyngeal wall.

FIG. 3 provides a view of a compromised airway, with an occlusion in thenasopharyngeal region due to posterior slippage of the soft palate.

FIG. 4 provides a view of a compromised airway, with an occlusion in theoropharyngeal region due to posterior slippage of the base of the tongueand the soft palate, a thickened posterior pharyngeal wall, andposterior flopping of the epiglottis.

FIG. 5 is a flow diagram of steps in a method for opening an airway withan obstruction that is causing obstructive sleep apnea.

FIGS. 6A1-6D2 show various embodiments of shape-changing devices orportions thereof that shorten after implantation. FIGS. 6A-1 and 6A-2depict a device that includes an expanded spring that is stabilized inan expanded configuration by an encasement of bioerodible material (FIG.6A-1); upon erosion of the bioerodible material, the spring returns to apreferred compressed configuration, thereby shortening the device (FIG.6A-2). FIGS. 6B-1 and 6B-2 depict a device that includes a stretchedsilicone rubber member that is stabilized in an expanded configurationby an encasement of confining and optionally adhering bioerodiblematerial (FIG. 6B-1); upon erosion of the bioerodible material, thesilicone rubber returns to a preferred retracted configuration, therebyshortening the device (FIG. 6B-2). FIGS. 6C-1 and 6C-2 depict a devicethat includes a collapsed lantern-like structure integrated into thelength of the device that is stabilized in that collapsed configurationby an encasement of bioerodible material (FIG. 6C-1); upon erosion ofthe bioerodible material, the laterally-constrained lantern members bowoutward in accordance with their preferred configuration, therebyshortening the device (FIG. 6C-2). FIGS. 6D-1 and 6D-2 depict a devicethat includes linearly constrained or confined resiliently deformablemember which has a preferred sine-wave shape (FIG. 6D-1); upon erosionof the bioerodible material, the linearly constrained member reverts toits preferred sine-wave shape, thereby shortening the device (FIG.6D-2).

FIGS. 7A-7H show various stages in a life cycle of an embodiment ofshape changing device that shortens after implantation, the device atvarious stages during its development and tenure. FIG. 7A shows aproto-device comprising a silicone rubber member with radiallyperipheral notches that ultimately will accommodate bioerodiblematerial, the member as a whole in its preferred shape, neithercompressed nor expanded. FIG. 7B shows bioerodible portions of thedevice ready for assembly, and FIG. 7C shows a cross section of thebioerodible portion of the device. FIG. 7D shows the proto-device ofFIG. 7A stretched into an expanded configuration, all linear portionsbeing expanded, particularly including the notches 105, which because oftheir smaller diameter, stretch more easily. FIG. 7E shows the deviceafter the incorporation of bioerodible material into the notches. FIG.7F shows a cross section of the device as depicted in FIG. 7E, with thebioerodible material surrounding the resiliently deformable material.FIG. 7G shows the device after a period of implantation, following theerosion of a portion of the bioerodible material, and a consequentshortening of the device.

FIG. 7F shows the device in its final state, following the completeerosive loss of such material, thus allowing the return of the siliconerubber to its preferred (non-stretched) configuration.

FIGS. 8A-8C show an embodiment of a shape-changing device that lengthensafter implantation by an outward bowing of a lantern-like portion. FIG.8A depicts a device in the process of being assembled, FIG. 8B shows thedevice in its implant-ready form, and FIG. 8C shows the device in itsmature form, following implantation, erosion of the bioerodiblematerial, and the device consequently in a lengthened configuration.

FIGS. 9A-9C show an embodiment of a shape-changing device that lengthensfollowing implantation by expansion of a spring. In a manner similar tothat shown in FIG. 8, FIG. 9A depicts a device in the process of beingassembled, FIG. 9B shows the device in its implant-ready form, and FIG.9C shows the device in its mature form, following implantation, erosionof the bioerodible material, and the device consequently in a lengthenedconfiguration.

FIGS. 10A-10C depict a rod-like shape-changing device or portion thereofthat forms a curve after implantation. In its nascent (FIG. 10A) formthe device is curved. In its implant-ready form (FIG. 10B) it isstraight. And in its post-implant, post-eroded form (FIG. 10C), it isonce again curved.

FIGS. 11A-11C depict a broadened planar shape-changing device or portionthereof that forms a curve after implantation. In its nascent form (FIG.11A) the device is curved, in its implant-ready form (FIG. 11B) it isstraight. And in its post-implant, post-eroded form (FIG. 11C), it isonce again curved.

FIGS. 12A-12C depict a rod-like shape-changing device or portion thereofwith a curve that flattens after implantation. In its nascent form (FIG.12A) the device is straight. In its implant-ready form (FIG. 12B) it iscurved. And in its post-implant (FIG. 12C), post-eroded form, it is onceagain straight.

FIGS. 13A-13C depict a broadened planar shape-changing device or portionthereof with a curved portion that flattens after implantation. In itsnascent form (FIG. 13A) the device is flat. In its implant-ready form(FIG. 13B) it is curved. And in its post-implant, post-eroded form (FIG.13C), it is once again straight or flat.

FIGS. 14A-14C show curvilinear shape-changing device or portion thereofwherein a curved portion is radially expanded. In its nascent andpreferred form the device is obtusely curved, in its implant-ready formit is more acutely curved, and in its post-implant, post-eroded form, itis once again more obtusely curved.

FIGS. 15A-15C show a rod-like shape-changing device or portion thereofthat assumes an S-shaped curve after implantation. In its nascent form(FIG. 15A) the device is forms an S-shaped curve. In its implant-readyform (FIG. 15B) it is substantially straight. And in its post-implant,post-eroded form (FIG. 15C), it once assumes an S-shaped curve.

FIGS. 16A-16C show a broadened planar-configured shape-changing deviceor portion thereof that assumes a planar S-shaped curve afterimplantation. In its nascent form (FIG. 16A) the device forms a planarS-shaped curve. In its implant-ready form (FIG. 16B) it is substantiallyflat. And in its post-implant, post-eroded form (FIG. 16C), it onceagain becomes a planar S-shaped curve.

FIGS. 17A-17C show a rod-like shape-changing device or portion thereofthat changes shape after the erosion of peripherally-attachedbioerodible suture. In its nascent form (FIG. 17A) the device is curved.In its implant ready form (FIG. 17B) the device is straight, secured bya suture extending the length of the device and secured at either end.In its post-implant, post-eroded form (FIG. 17C) the device is onceagain curved.

FIGS. 18A-18E show bowl-shaped shape-changing device or portion thereofthat assumes a disk-like shape after implantation. In its nascent formthe device has a bowl-like portion. In its nascent form (FIG. 18A), thedevice is bowl-shaped. As it is being formed (FIG. 18 b) into an implantready device, it is flattened and combined with bioerodible material. Inits implant-ready form (FIG. 18C), it has taken a disk-like shape. FIG.18D shows a cross-sectional portion of the disk-like form, withbioerodible material constraining the device as whole in a flatconfiguration. In its post-implant, post-eroded form (FIG. 18E), thedevice or portion thereof has returned to a bowl-like configuration.

FIGS. 19A and 19B provide sagittal views of an airway that are used asreference for the coronal views of FIGS. 20A and 20B. FIG. 19A depictsan airway with an occlusion due to thickening and shortening of theposterior pharyngeal wall before treatment. FIG. 19B depicts with airwaywith an implanted shape-changing, linearly-expanding device that hasresolved the obstructed region.

FIGS. 20A and 20B provide coronal, downward-directed views of theairways depicted in FIGS. 19A and 19B. FIG. 20A shows an airwayobstructed by a compressed posterior pharyngeal wall, and FIG. 20B showsthe resolution of the compression by the implantation of acurve-expanding shape-changing device.

FIG. 21 shows a schematic cutaway view of a portion of a pharyngeal wallthat has been expanded by the implantation of a series ofcurve-expanding devices.

FIGS. 22A-22C show sagittal views of an airway obstructed by posteriorslippage of the soft palate, and resolution of the obstruction by theimplantation of a shape-changing device that provides a caudally and/oranteriorly deflecting curve to the soft palate.

FIGS. 23A and 23B show schematic views of a soft palate being treated bythe implantation of a shape-changing device that provides a caudallyand/or anteriorly deflecting curve to the soft palate.

FIGS. 24A and 24B show sagittal views of an airway obstructed byposterior slippage of the base of the tongue, and resolution of theslippage by a shape-changing device that is hard-anchored in the jaw andharnessed to the hyoid bone, and pulls or advances the hyoid toward thejaw by becoming shorter.

FIGS. 25A and 25B show sagittal views of an airway obstructed byposterior slippage of the base of the tongue, and resolution of theslippage by a shape-changing device that is hard-anchored in the jaw,engages tissue at the base of the tongue, and pulls the tongue towardthe jaw by becoming shorter.

FIGS. 26A and 26B provides a detailed view of a device embodiment thatmay be used as an alternative to the device shown in FIG. 25.

FIGS. 27A and 27B show an embodiment of a shape-changing device that isinserted into tongue tissue, anchored at a site on the inner aspect ofthe jaw, and changes shape in a curvilinear manner, drawing the tongueanteriorly as a whole, and superiorly, particularly at the base. FIG.27A shows the device upon implantation; FIG. 27B shows the device afterbioerosion and changing shape.

FIGS. 28A and 28B show another embodiment of a device that may be usedalternatively to the devices shown in FIGS. 24-27 for pulling the baseof the tongue forward toward the jaw.

FIGS. 29A-29C show an embodiment with a shape-changing profile similarto that of the embodiment depicted in FIGS. 11A-11B, this embodimenthaving an alternative profile for the bioerodible material component.

FIGS. 30A-30D show an embodiment of a shape-changing device similar tothat of FIGS. 9A-9C in that it lengthens following implantation andsubsequent erosion of bioerodible material. The present embodiment,however, constrains a spring in a compressed configuration by securingit with bioerodible sutures. FIG. 30A shows a nascent device in itspreferred configuration. FIG. 30B shows the device at an implant-readystage, the spring secured in a compressed state by bioerodible sutures.FIG. 30C shows the device following implantation and in a state ofpartial erosion of bioerodible material and in a partially expandedstage. FIG. 30D shows the device after complete erosion of bioerodiblematerial, and in a fully expanded state, a shape that substantiallycorresponds to the original and preferred shape of the device.

FIGS. 31A-31D show a device that has a three-dimensionally curvedconfiguration when at an implant ready stage, and that flattens uponerosion of bioerodible material. This device is, to some extent,functionally the complement of the device depicted in FIGS. 18A-18E, inthat the previous (FIG. 18) device is in a flat configuration atimplant, and assumes a three-dimensional bowl-like configurationfollowing implantation and bioerosion. FIG. 31 shows the device at anascent stage where it is flat, and has leaf-cuts included toaccommodate being curved. FIG. 31B shows the device after being formedinto a bowl-like shape, such shape stabilized by the incorporation ofbioerodible material into slots on the outer surface of the curve, asshown in the cross-sectional view of FIG. 31C. FIG. 31D shows the devicein the flattened shape it returns to following implantation and erosionof the bioerodible material. This embodiment also features holes 108 fortissue engagement or in-growth, such in-growth engaging the tissueimplant site and the device such that the tissue tends to adhere to thedevice while the device changes shape, rather than pulling away from it.

FIGS. 32A and 32B show applications of shape-changing devices, asdepicted in FIGS. 18 and 31, as they are implanted into the base of thetongue, where they each create a shape-change in remodeling that bringsthe tongue forward, thereby opening the airway behind it. FIG. 32A showsflat but bowl-forming device implanted in the base of the tongue. FIG.32B shows the device at a time period following implantation,bioerosion, and consequent shape change in the form where the creationof an anteriorly directed curve has formed.

FIGS. 33A and 33B show a three-dimensionally curved device, convexsurface facing anteriorly in situ in the base of the tongue. FIG. 33Ashows the device in situ, immediately after implantation. FIG. 33B showsthe same device at a point in time after implantation, bioerosion, andsubsequent shape change in the form of a flattening of the threedimensional curve that pulls tissue forward, expanding the airwayopening behind the tongue.

DETAILED DESCRIPTION A. Anatomy of the Pharynx

FIG. 1 is a sagittal view of the structures that form the pharyngealairway 4; some of these structures can become compromised under variousconditions to the extent that they obstruct or occlude passage of airthrough the airway 4, and thus contribute to obstructive sleep apnea.The pharynx is divided, from superior to inferior, into the nasopharynx1, the oropharynx 2 and the hypopharynx 3. Variations of FIG. 1 areprovided in FIGS. 2, 3, and 4, which depict airway obstruction sites 5at various levels in the pharyngeal airway. FIG. 2, for example, showsan occlusion 5 at the level of the oropharynx 2, where the base of thetongue 16 and a thickened posterior pharyngeal wall 22 have collapsedagainst each other. FIG. 3 shows an occlusion 5 at the level of thenasopharynx 1, where an elongated and/or floppy soft palate hascollapsed against a thickened posterior pharyngeal wall. FIG. 4 shows anocclusion 5 at the level of the hypopharynx 3, where both an elongatedsoft palate and a floppy epiglottis have collapsed against thepharyngeal wall 22.

With reference to FIGS. 1-4, the nasopharynx is the portion of thepharynx at the level or above the soft palate 6. In the nasopharynx, adeviated nasal septum or enlarged nasal turbinates may occasionallycontribute to upper airway resistance or blockage. Rarely, a nasal mass,such as a polyp, cyst or tumor may be a source of obstruction. Theoropharynx 2 includes structures from the soft palate 6 to the upperborder of the epiglottis 12 and includes the inferior surface of thehard palate 14, tongue 16, tonsils 18, palatoglossal arch 20, theposterior pharyngeal wall 22 and the mandible 24. The mandible typicallyhas a bone thickness of about 5 mm to about 10 mm anteriorly withsimilar thicknesses laterally. An obstruction in the oropharynx 2 mayresult when the tongue 16 is displaced posteriorly during sleep as aconsequence of reduced muscle activity during deep or non-REM sleep. Thedisplaced tongue 16 may push the soft palate 6 posteriorly and may sealoff the nasopharynx 1 from the oropharynx 2. The tongue 16 may alsocontact the posterior pharyngeal wall 22, which causes further airwayobstruction.

The hypopharynx 3 includes the region from the upper border of theepiglottis 12 to the inferior border of the cricoid cartilage 14. Thehypopharynx 3 further includes the hyoid bone 28, a U-shaped,free-floating bone that does not articulate with any other bone. Thehyoid bone 28 is attached to surrounding structures by various musclesand connective tissues. The hyoid bone 28 lies inferior to the tongue 16and superior to the thyroid cartilage 30. A thyrohyoid membrane 17 and athyrohyoid muscle 18 attaches to the inferior border of the hyoid 28 andthe superior border of the thyroid cartilage 30. The epiglottis 12 isinfero-posterior to the hyoid bone 28 and attaches to the hyoid bone bya median hyoepiglottic ligament. The hyoid bone attaches anteriorly tothe infero-posterior aspect of the mandible 24 by the geniohyoid muscle.

B. Method of Opening an Obstructed Airway with ImplantableShape-Changing Devices

Embodiments of the invention include methods for opening a collapsed orobstructed airway with devices that can be implanted into varioustissues that form the airway. Embodiments of the devices includeresiliently deformable materials and bioerodible materials. Thedeformable portion of the devices, when first formed, is formed into apreferred shape which is then subsequently deformed, and stabilized inthat deformed shape by incorporation or application of bioerodiblematerials to create a device in its implantable form. Once implantedinto a tissue site, and thus exposed to an aqueous environment andsubject to cellular and enzymatic action, the bioerodible portions ofthe device erode, thereby allowing the deformable portion of the deviceto return toward the preferred form. Embodiments of the method, in theirsimplest form, thus include implanting a device, the bioerodible portionof the device bioeroding, the device changing shape as a consequence ofthe bioeroding, and the tissue remodeling in accordance with the forcebeing exerted by the shape changing of the device. Reciting the methodin a more complete form, it may be understood that the method oftreating sleep apnea or treating the underlying obstruction thatprovokes the sleep apnea, may begin by forming the device to beimplanted. These methods are broadly depicted in FIG. 5, as describedbelow.

FIG. 5 depicts various steps in a method for treating sleep apnea, asdescribed in basic form above, wherein a bioerodible device is formed,implanted, and tissue thereby beneficially reformed by the presence ofthe device. In a Step 510, a device that may be considered a preliminarydevice, or a proto-device, or a device in its initial form is formedfrom materials that include, or substantially include the deformablematerials that will be present in the final form of the device. Thepreliminary device is formed into a shape by casting or other methodswell known in the art into a shape that is preferred, a shape to whichthe device will return absent constraints or conditions that preventsuch return. Embodiments of the proto-device typically include sites orfeatures that will later be occupied by bioerodible materials.

In Step 520, the proto-device is shaped into a deformed shape orconfiguration that corresponds to what will be the final shape of animplant-ready device. Such deforming of the proto-device may also alteror create sites or features that will accommodate the bioerodiblematerials.

In Step 520, the shape-memory material-based proto-device is combinedwith, or receives the bioerodible materials. As will be described below,such incorporation of bioerodible materials may occur in various ways.For example, the bioerodible materials may fill in vacant sites such asinlets, pores, or holes; in other embodiments, the bioerodible materialsmay be built up on top of deformable materials, or the proto-device maybe partially- or fully-encased in a layer of bioerodible materials. Insome embodiments, the bioerodible materials may be soft or malleablewhen being combined with deformable materials. In these embodiments,after combining the deformable proto-device with bioerodible materials,a hardening or curing step may be needed to complete formation of astable device. In other embodiments, the bioerodible materials may berigid or hard, in which case, after inserting bioerodible pieces, orsnapping them into place, the device may assume a substantially finalform. In some embodiments of the method, Steps 2 and 3 may be integratedor overlapping to the extent that there is no demarcation between them.

In Step 530, the completed and implant-ready device is implanted in atissue site, the tissue being any of several that form portions of theairway, such as, by way of example, the soft palate, a site in thepharyngeal wall, or the tongue. Tissue implantation is typically anatraumatic insertion, and has a minimal immediate effect on the shape orconformation of the implantation site.

In Step 540, the bioerodible portion or portions of the implanted deviceerode. This erosion occurs by virtue of the device being in the aqueousbiological environment, at body temperature, and being subject to attackby cells of the immune system and enzymes present in the interstitialfluid. As the bioerodible portion(s) of the device erode, theshape-memory portion of the device becomes increasingly loosed from theconstraints imposed by the previously confining or constrainingbioerodible materials, and the device begins to change shape toward thepreferred shape (Step 550). The time course or rate of the shape-changevaries according to the particulars of the embodiment. However, suchvariation in shape-change rate is controllable by varying features suchas the thickness, volume, or accessibility of the bioerodible materials,and the rate is predictable, based on empirical observations from invitro model systems and in vivo studies.

Also occurring after implantation, and typically at a faster rate thanshape change, is the biological reaction of host tissue to the presenceof a foreign body. Such reaction includes formation of fibrotic tissuethat, in time, substantially encases the implant. The fibrotic tissuestabilizes the device within the host site, and is a form of tissuehealing following the disruption or injury associated with implantation.The fibrotic response provides a level of traction between the deviceand tissue that allows the shape change of the device to graduallychange the shape of the host site, and to effectively reform it. Thisgradual rate of tissue shape reforming, over a time course that variesfrom days to months, is advantageous, and stands in contrast to animplant that corresponds to the intended post-implant configurationimmediately, or that changes shape more quickly than the site canactually accommodate such change. In cases of immediate or too-soonshape change, the implanted device may be at risk for cutting or erodingthrough host tissue, instead of actually reforming or therapeuticallyremodeling it; and in more extreme cases, a device may disrupt orextrude from the implant site.

The stabilization of the device in the desired tissue site by suchfibrotic tissue can be enhanced, as described further below, bytissue-interactive, tissue-adhering, or tissue-engaging features of thedevice embodiments. Such device features may include, for example, sitesof tissue intercalation, whereby fibrotic tissue becomes enmeshed orgrows into or through sites of the device. Embodiments oftissue-engaging sites such as these may be described as holes or pores,and may either dead-end into a device surface or penetrate entirelythrough a portion of a device. Tissue-interactive aspects of may alsoinclude features that simply increase the surface area to volume ratioof portions of device embodiments, the increased surface area providinga scaffolding or simply more surface for fibrotic tissue to cover or toincorporate into, or greater associated volume of tissue to engage.

In Step 560, the tissue surrounding the implant site becomes remodeledin accordance with the changing shape of the device. The change in shapewill vary according to particulars of the implant site and the device,and the preferred shape of the device. Despite such variation, whatembodiments of the method have in common is that such changes in tissueshape will counteract the dysfunctional shape changes that had lead tothe airway occlusion, and, accordingly, the embodiments will increasethe opening provided by the airway such that air flows therethrough moreeasily, at a higher rate per unit airway pressure. The remodeling oftissue is such that the increased opening of the airway is substantiallymanifests during sleep. Step 560 (tissue shape changing) follows as aconsequence of Step 550 (device shape changing), and can, to someextent, lag behind Step 550. However, the processes associated withSteps 550 and 560 generally proceed coincidentally, i.e., as the devicechanges shape, force is released by such change and is absorbed by thesurrounding tissue, encouraging the tissue to remodel so as to conformto the device.

C. Shape Changing Devices that are Implantable in Tissues of the Airway

The shape-changing of devices that include deformable or shape-memorymaterials 100 and bioerodible materials 107, as provided in specificembodiments described further below, proceeds by way of various types ofchanges in shape, and by combinations of such approaches. Shapechanging, as performed by device and method embodiment described herein,happens with implantable devices over a period of time after they areimplanted, as a result of erosion of the bioerodible portion of thedevice. At the time of implantation, the devices are in a shape orconfiguration that is different from that of a preferred shape orconfiguration, such preferred shape substantially defined by theresiliently deformable portion of the device.

The nature of the shape-change, once-implanted is toward the shape orconfiguration that is preferred by the deformable or shape-memoryportion 100 of the device, such shape change being facilitated by theerosion of bioerodible material 107 that (until erosion) had beenconstraining the device in a non-preferred or deformed shape. Thegradual aspect of shape change that embodiments of the device undergo isby an intended feature of the device design, and is advantageous in thatit facilitates a gradual and effective remodeling of tissue surroundingthe implant site. Another aspect of embodiments of the shape-changingdevices is that the resiliently deformable material, once loosed frombioeroded constraints, remains at least substantially as flexible as itwas when it was in the form of the proto-device, prior to theincorporation of bioerodible material. Such flexibility imparts aforgiving aspect to the stabilization of shape that the device impartsto the remodeled tissue. The airway-forming tissues, such as, by way ofexample, soft palate, tongue, or pharyngeal wall, are all soft tissues,that flex within a range of shapes during the movements associated withswallowing and breathing, and also as a function of bodily position,such as when the individual is standing or reclining. Thus, changing theshape of portions of the airway, as provided by embodiments of theinvention, may be appropriately understood as shifting the range ofshapes that such tissues assume dynamically as part of their anatomicalform, serving their physiological function.

Still another aspect of embodiments the shape-changing devices andmethods of changing shape relates to an appreciation of two classes offorce that are exchanged between the device and the host tissue site asthey engage each other. One aspect of force exchange involves the forceload kinetically applied to the proto-device in its preferred shape inorder to force it into a non-preferred shape that is then held in placeas potential energy by the bioerodible material. This amount of forcemay be considered a force of a level F1. This force F1, corresponding tothe force associated with maintaining the device in its non-preferredshape, is also that which is released gradually by the device into thetissue, over a time course that may range up to several months, forexample. This force F1 is what is responsible for the remodeling of thetissue site, as it is transferred from the device to the tissue sitethat absorbs it.

Thus, force that is required to effect the change of shape of a nascentdevice from its preferred shape to the non-preferred shape of theimplant ready device is a level of force sufficient to remodel an airwaysuch that it is unobstructed during sleep, as such force F1 is releasedinto and absorbed by the tissue site. However, the force F1 imparted tothe tissue site may not exceed a level sufficient to remodel the airwayto the extent that the site or surrounding tissue is unable to move in amanner that allows normal or near-normal physiological function.

A second aspect of force exchange between the device and the tissue sitemay be called F2, which is represented by the level of force that thetissue site imparts on the device, and which the device absorbs by wayof the resilience or elasticity of the device as a whole. Absorbing F2is thus a property of the material device design which is substantiallyindependent of the preferred-non-preferred shape status of the device,and follows from the materials that comprise the device and the overalldevice design. As a simple example of design or shape of the deformableportion of the device that affects the overall elasticity of the devicewithin the host tissue site, a thin device will be more elastic than athick device of the same material. Force F2 thus engages the resilienceor elasticity of the device with respect to the movement that itundergoes as it responds to normal physiological movement of the implantsite, and is an important feature of the behavior of the device withintissue that is dynamically changing as part of its normal function.

Embodiments of the inventive device and method appropriately balance theforces F1 and F2 with respect to the device, the amount of desiredshape-change to be imparted to the host tissue, and the amount ofmovement and shape-changing inherent to natural and proper functioningof the host tissue site. By way of example, with an excessive amount ofshape-changing force F1, it would be easy to pull the base of thetongue, as in embodiments shown in FIGS. 24-28 too far forward,overwhelming force F2, and this could interfere with swallowing. With adevice too stiff, it would also be easy to disallow natural movement ofthe tongue during swallowing. In general, the amount of force F1 neededto effect tissue shape-changing is relatively small compared to the verystrong muscular forces (corresponding to F2) involved in swallowing.Accordingly, embodiments of shape-changing devices provided herein aredesigned with an appropriate level of potential energy corresponding toF1 and an appropriate level of elasticity of the device as a whole,corresponding to F2, to be compatible with normal tissue function. Theappropriate levels of F1 and F2 may be independent of each other, but insome embodiments the appropriate levels may have a relationship, eitherpositive or negative. In embodiments where such a relationship exists,there further being an appropriate ratio or function that that relatesF1 and F2 to each other.

Device Materials

Resiliently deformable or elastic materials that comprise the deformableportion of embodiments of the device may include plastics or metal thatcan be forcibly deformed from an initial or preferred shape to adeformed or contorted shape, and then, by virtue of their materialproperties, return to the preferred shape upon release of deformingforce or constraint. Deformable plastics appropriate for devicesdescribed herein are well known in the art and may include, merely byway of example, silicone rubber (Silastic®), polyesters, polyurethanes,and/or polyolefins. Resiliently deformable metals appropriate fordevices described herein may include, merely by way of example,stainless steel, spring steel, and shape-memory, superelastic metalssuch as nickel-titanium alloy (NiTi, Nitinol). The resilientlydeformable portion of embodiments of the device may also be formed fromcombinations of materials, such as, merely by way of example, elasticpolymer portions with Nitinol wire embedded therein.

Bioerodible materials may be understood as any material that erodes,degrades, is absorbed, is resorbed, or loses its structural integritywhen exposed to a biological environment. Bioerodible materials aretypically polymers, both natural and synthetic, such as, merely by wayof example, polycaprolactone, polylactic acid, polyglycolic acid,polylactide coglycolide, polyglactin, poly-L-lactide,polyhydroxalkanoates, and polysaccharides such as starch, cellulose, andchitosan, as well as structural proteins such as, merely by way ofexample, collagen. Some particular embodiments may include calciumcarbonate-based ceramic materials; a contemporary example of anappropriate material is a resorbably beta-tricalcium phosphatemanufactured by Orthovita (Malvern, Pa., USA), as further formulatedwith collagen and synthetic polymers by Kensey Nash Corporation (ExtonPa., USA). Further, as with the resiliently deformable portion of deviceembodiments, the bioerodible portion of device embodiments may includecombinations of such materials.

The rate at which bioerodible materials are degraded in the body variesaccording to the composition of the material, but may be testedempirically in model systems so that it becomes predictable. Further,the rate of erosion of a region of bioerodible material can becontrolled by the configuration and exposure of the material. Forexample, larger or thicker regions will degrade more slowly than smalleror thinner regions. The ratio of exposed surface area-to-volume willaffect the rate of degradation of the erodible site as a whole. In someembodiments, it may be advantageous to configure separate bioerodibleregions within a device such that they degrade at differing rates.Further design features that may provide control or predictability withregard to bioerosion include the incorporation of areas particularlysusceptible to erosion, such sites being deliberately designed andpositioned points of failure or frangibility. With bioerosion staged insuch a way, the resiliently deformable materials may be released fromerodible material constraints in a programmed or step-by-step manner.Methods of forming units of bioerodible polymer are well known in theart, and generally include processes such as molding or profileextrusion.

Bioerodible materials within embodiments of the implantable device, inaddition to their utility for degradation and removal from the implanteddevice per se, may also be advantageously utilized for the delivery ofelutable bioactive agents. Bioactive agents such as drugs or hormonesthat are eluted during the course of erosion of the bioerodiblematerials, may serve, for example, to promote healing of the implantwound, or to promote stabilization of the implanted device within thetissue site by, for example, promoting the toughening the fibrotictissue capsule that forms around the implanted device.

Types of Shape Changes

Shape-changing devices described and depicted herein (FIGS. 6-29) hereincan be broadly understood as having a life cycle that takes them throughthree basic stages. Shape changing devices described herein, regardlessof the particulars of form, or stage within manufacturing orpost-implant status or intended implant site may be generally referredto as a device 200. The initial stage of a device 200 may be variouslyreferred to simply as a “device”, “proto-device”, “nascent device” andis that of a device in a pre-implant ready form or, in some instances, akit or exploded assembly of parts which may be so-labeled. In someembodiments, the nascent device is simply the resiliently deformableportion 100 of the device in its preferred shape or configuration,before the incorporation of bioerodible material 107. A complete kit orproto-device 200 may further include the bioerodible material itself ina form that is prepared for incorporation into a device, as well as anyancillary parts, such as a tissue stabilizing end bar or end piece 205,or a tissue connector 111, such as a screw.

The second stage of the device is an implant-ready device 200′, whichincludes the resiliently deformable material after having been placedinto a non-preferred shape, i.e., the shape appropriate for implantationinto a site in an airway-forming tissue, or an implant-ready shape. Asthe method description above has set out, the process of making a deviceincludes putting the resiliently deformable portion of the proto-device200 into an appropriately contorted or deformed shape, and combiningthat portion with bioerodible material 107. The incorporated bioerodiblematerial 107 stabilizes the resiliently deformable material of theproto- or nascent device in the deformed shape. The complete andimplant-ready device 200′ thus includes the resiliently-deformablematerial and the bioerodible material combined together. The bioerodiblematerial may be incorporated more specifically into specific sites 105within the resiliently-deformable material. The complete implant-readydevice 200′ may further include any ancillary features such as tissuestabilizing features 205 or tissue connectors 207.

After implantation of a device 200′, the erodible material 107 withinaccommodating sites 105 begins to erode, and with such erosion, thedevice as a whole begins to change shape, ultimately arriving at a finalstate 200″, a shape that is substantially determined by the preferredshape of the resiliently deformable portion 100 of the device. Thisfinal shape of the device in situ, (or more particularly, the range offinal shapes, per the general description of shape-changing devices,above) as compared to the non-preferred shape, is thus toward that ofthe preferred shape, as manifested by the shape of the proto-device 200.In some embodiments, the final shape of device 200″ may be substantiallyidentical to that of nascent device 200, in other embodiments thechanged shape may not fully return to that of the nascent device 200.The degree of similarity or dissimilarity between the shape of thenascent device 200 and the implanted and post-bioeroded device 200″ maybe a function of variables such as the resilience of the resilientlydeformable portion 100 of the device, and of the amount of resistanceprovided by the host tissue into which the device is implanted.

Another aspect of change of shape or configuration of device isassociated with the shape or condition of the bioerodible materialaccommodating sites or slots 105 that may be present in the nascentdevice 200, the implant ready device 200′, and the post-eroded device200″. The shape of the empty sites 105 in the nascent device 200 willvary according to the configuration of the device as a whole, butgenerally the empty sites 105 will have the form of slots or compressedor flattened space. The shape of the bioerodible material-filled sites105′ will be their fullest form. The shape of the empty, post-erosionaccommodating sites 105 in the shape-changed device 200′ substantiallyreturns to that of the sites 105 in the nascent device. Some embodimentsof a proto-device 200 may not have a discrete bioerodiblematerial-awaiting site, but the bioerodible material-occupied site 105may form a broader feature or aspect or portion of an implant-readydevice, as for example when the bioerodible material is an encasement,covering or filling the device, either in part or as a whole, as seen,for example, in embodiments shown in FIG. 6. Further, as describedabove, in some embodiments, the bioerodible material may provide areservoir of bioactive agents that are gradually released from thematerial as it erodes. Device embodiments that make use of an encasinglayer of bioerodible material may be particularly appropriate foreluting bioactive agents into the implant site, encouraging a beneficialhealing response.

The description will now turn to a basic description of the geometricaspect of various types of shape-changes devices 200′ may undergofollowing their implantation into tissues lining the airway. Devices mayshorten (FIGS. 6 and 7) or lengthen (FIGS. 8 and 9), and such shorteningor lengthening may occur in the context of a substantially linear orrod-like device, or a linear portion of a device, and such shortening orlengthening may further occur in the context of a linear dimension of asubstantially planar device, or planar portion of a device. Typically,the shortening of an implanted device serves to pull or compress tissuethat is adherent to the device, or connected to the ends of an implanteddevice by specific features of the device. Examples of embodiments wherea device that shortens and effects a shape change by pulling anchoringsites from two tissues together is described below where an embodimentof an implanted device is anchored at one end to the hyoid bone and atthe other end at a site in the mandible (FIG. 24), the shortening of thedevice causing the base of the tongue to move forward, thereby openingthe airway. In another example, an embodiment of an implanted device isanchored at one end in tissue at the base of the tongue and at the otherend at a site in the mandible (FIGS. 25-28), the shortening of thedevice (as in the preceding example), causing the base of the tongue tomove forward, thereby opening that local portion of airway. Shorteningor lengthening of a device, described above basically in the context ofa single dimension, may also occur in two dimensions. For example,depending on particulars of structure, a device embodiment could expandor contract along an x-axis and a y-axis. In some embodiments, expansioncould occur along one axis, and contraction could occur along the otheraxis. Further, the axes need not be perpendicular to each other. Theeffect of these variations of shape change along separate axes maymanifest in expansion or contraction of surface areas, which may furthercause shape change in a third dimension.

Devices may also change shape by forming curves once implanted andbioeroded (e.g., FIGS. 10, 11, 15, 16), and such curve-forming may occurin the context of a substantially linear or rod-like device, or a linearportion of a device. Such curve-forming may also occur in the context ofa linear dimension of substantially planar device, or planar portion ofa device. Curve forming may occur in complex linear patterns as well, arod-like device, for example, may vary in the degree of curvature alonga linear section, and curves may occur in alternate directions along alinear portion of a rod so as to create S-shaped curves, or multipleS-shape curves, in a sine-wave like manner.

Devices may also change shape by flattening already-formed curves (e.g.,FIGS. 12 and 13). Such curve flattening may occur in the context of asubstantially linear or rod-like device, or a linear portion of adevice, and such curve-flattening may occur in the context of a lineardimension of substantially planar device, or planar portion of a device.In a converse manner to the formation of S-shaped sections, or sine-wavesections, such complex curves may be flattened wholly, or to varyingdegree.

Curve forming may also occur across two and three dimensions, as forexample, a flat or planar device, or a planar portion of a device, maychange shape so as to form a cup-like shape (e.g., FIG. 18), a convex-or concave portion, depending on the perspective from which the deviceis observed. Similarly, curve flattening may also occur across two orthree dimensions (e.g., FIG. 31), as for example, a two-dimensionaldevice, or a substantially two-dimensional portion of a device, maychange from a cup-like shape (a convex- or concave portion, depending onthe perspective from which the device is observed) to a flattened shape.

Illustrating Shape Changes

The shape-changes of devices implantable in tissues that form theairway, as described in basic geometric terms above, will now bedescribed and depicted more specifically as they are created by variousdevice embodiments. FIGS. 6A-6D and 7 show various approaches by whichan implantable device comprising resiliently deformable material andbioerodible material can change shape by shortening. In these and otherfigures, label 100′ refers to resiliently deformable material in itsnon-preferred state, such as being expanded, and label 100 refers to theresiliently deformable material after having returned to its preferredstate, such as being non-expanded. Label 105 refers to a site forbioerodible material that is empty either for not yet being filled orfor the bioerodible material having been eroded, and label 105′ refersto a site that is filled with bioerodible material. Further, as notedabove, label 200′ refers to a device in its implantable state, in anon-preferred configuration per the resiliently deformable portion ofthe device, and 200″ refers to the same device after bioerosion and areturn toward the preferred shape per the resiliently deformable portionof the device. FIGS. 6A-1 and 6A-2 depict an embodiment wherein device200′ includes a deformable component in the form of a spring that isconstrained in an expanded configuration by an encasement of bioerodiblematerial. After erosion of the bioerodible material and consequent shapechange, device 200″ emerges, which is shorter than device 200′ as aconsequence of the spring-form deformable material resiliently returningto its preferred non-expanded shape.

FIGS. 6B-1 and 6B-2 depict an embodiment similar wherein the siliconerubber core is stretched and then encased in layer of bioerodiblematerial which holds the core in that stretched configuration (FIG.6B-1, device 200′). In some embodiments a broad mutual adhesion betweenthe silicone rubber material and the bioerodible material contributes tothe constraining in this configuration; in other embodiments, theerodible and deformable portions may not necessarily be mutuallyadherent. Following a period of implantation and consequent erosion ofthe bioerodible material, device 200″ (FIG. 6B-2) emerges, which isshorter than device 200′ as a consequence of the silicone rubbermaterial contracting to its preferred and shorter state.

FIGS. 6C-1 and 6C-2 depict an embodiment of device 200′ wherein alantern-like arrangement of deformable materials is held in alaterally-compressed configuration by a wrapping or encasement within alayer of bioerodible material. The lantern-like structural componentshave a preferred bowed-outward shape that emerges as the bioerodiblematerial erodes, allowing the deformable components to resiliently bowoutward, and thus contract the device in its linear dimension, andcausing the emergence of device 200″.

FIGS. 6D-1 and 6D-2 depict an embodiment of device 200′ wherein aNitinol-based central component that includes one or more curves in apreferred state, but the component is held in a linear configuration bya shape-constraining encasement of bioerodible material. Upon erosion ofthe bioerodible encasement, the Nitinol core assumes its preferred andmultiply-curved configuration, causing the emergence of device 200″,which is shorter than its parent form 200′.

FIGS. 7A-7G depict a shortening device in some considerable detail overthe course of its life cycle. As in FIG. 7A, an embodiment of device 200includes a silicone rubber component in the form of a central core withintervening circumferentially peripheral notches or available sites forthe inclusion of bioerodible materials, as well as bioerodible materialsegments 107 configured to fit within the slots 105, circumferentiallyaround the narrowed rod portions. Reference line 7B identifies thelocation of cross section seen in FIG. 7B. Reference line 7C identifiesthe location of the cross section seen in FIG. 7C. In FIG. 7D, thedevice has been stretched into an expanded configuration (anon-preferred shape). It can be seen that the slots, in particular, areexpanded over their length seen in FIG. 7A.

In FIG. 7E, the segments of bioerodible material 107 have been fittedinto the slots 105, to form an implant-ready device. Reference line 7Fof FIG. 7E identifies the location of cross section seen in FIG. 7F.FIG. 7G shows the device as it would appear in situ after a period oftime that has allowed a degree of partial erosion of the bioerodiblematerial 107. It can be seen that in this particular embodiment, partialerosion has created a partial shortening of the regions of the deviceoccupied by the bioerodible material. Finally, FIG. 7H shows a device200″ in which all of the bioerodible material has eroded away, leaving adevice now substantially consisting of the silicone rubber material, andnow returned to its preferred and contracted or shorter length.

FIGS. 8 and 9 show exemplary approaches by which an implantable devicecomprising deformable material and bioerodible material can change shapeby lengthening. FIG. 8A shows a proto-device 200 at a point during itsfabrication. In this particular embodiment the resiliently deformableportion includes lantern like-forming regions that can accommodatebioerodible material where components can be forced to bow outwardthereby (1) shortening the total length of the device, and (2) creatinga site 105 that can accommodate a unit of bioerodible material 107,which, once placed in the site, stabilizes the lantern-like bowed-outcomponents in their bowed configuration. The preferred state of thelantern-like components is a straight configuration, as depicted in theupper portion of the device 200. FIG. 8B shows the device in itsimplant-ready form 200′, with two bowed-out regions, each stabilized bythe inclusion of a bioerodible unit contained therein. FIG. 8C shows thedevice in its post-eroded form 200″, wherein the bioerodible units havebeen eroded away, thus allowing the lantern-like bowed-out regions tolaterally compress into their preferred shape, and thus lengthening thedevice as a whole with respect to the parent device 200′.

FIGS. 9A-9C show an embodiment of a shape-changing device that lengthensfollowing implantation by expansion of a spring at various stages in itslife cycle. In a manner similar to that shown in FIG. 8, FIG. 9A depictsa device kit 200 in the process of being assembled from the resilientlydeformable portion of the device 100 in the form of a spring, and withtissue stabilizing end pieces 205, and the bioerodible material 107standing by. Also shown is an empty accommodating space for thebioerodible material 105. FIG. 9B shows the assembled device 200′ in itsimplant-ready form, with the spring-form portion 100′, now compressed,the bioerodible material 107 in place within coils of the spring. FIG.9C shows the device 200″ in its mature form, following implantation, thebioerodible material now eroded and gone, and the device consequently ina lengthened configuration.

FIGS. 30A-30D show an embodiment similar to that depicted in FIGS. 9A-9Cin that the device 200′ lengthens upon implantation and erosion ofbioerodible material that holds a spring-like mechanism in a compressedstate. In the present embodiment, however, rather than having anencasement of bioerodible material, the material is in the form ofbioerodible sutures 107. FIG. 30A shows the device in its nascent form200, with the deformable material in its preferred, non-compressed form.FIG. 30B shows the device 200′ in its implant-ready form, with theresiliently deformable material in a compressed form, held by sutures107′. FIG. 30C shows the device 200′ in a partially eroded andconsequently partially-expanded form. FIG. 30D shows device 200″ in itsmature form, expanded toward its original and preferred shape per theresiliently deformable material, with the bioerodible suture materialnow gone. The use of bioerodible sutures is also seen in the deviceembodiments depicted in FIG. 17, below. In the present embodiment,sutures may connect the respective ends of the compressed device, andthey may also connect the compressed portion of the device at variousintermittent locations. Further, such segmented constraints, here, inthe form of sutures, may vary amongst each other with regard to theirresistance or susceptibility to bioerosion. The effect of variable ratesof erosion in such an arrangement is that the device can expand instages, as constraints erode at their varied rates. Erosion rates can bevaried by a number of approaches and combinations thereof, such as, forexample, the use of varied materials, or by varying, for example, thethickness of sutures of identical material.

FIGS. 10 and 11 show exemplary approaches by which an implantable devicecomprising resiliently deformable material and bioerodible material canchange shape by forming a curve. FIG. 10A shows a linear proto-device200 that is comprised of deformable material in its preferred curvedconfiguration, with sites 105 for the insertion of bioerodible materialpieces 107. FIG. 10B shows an implant-ready device 200′, with thebioerodible material 107 included in the sites 105 within the deformableportion 100 of the device. By such insertion, the device 200 has beenforced to assume a straight configuration. FIG. 10C shows the device,now in configuration 200″ following the erosion of the bioerodiblematerials, and by such erosion, the deformable portion has been freed toresume its preferred configuration, giving the device 200″ a curvedshape.

FIG. 11A shows a planar proto-device 200 that is comprised ofresiliently deformable material in its preferred curved configuration,with linear sites 105 for the insertion of bioerodible material pieces107. FIG. 11B shows an implant-ready device 200′, with the bioerodiblematerial 107 included in the sites 105 within the deformable portion 100of the device. By such insertion, the device 200′ has been forced toassume a straight planar configuration. FIG. 11C shows the device, nowin configuration 200″ following the erosion of the bioerodiblematerials, and by such erosion, the deformable portion has been freed toresume its preferred configuration, giving the device 200″ a curvedplanar shape.

FIGS. 29 A-29C show an embodiment with a shape-changing profile similarto that of the embodiment depicted in FIGS. 11A-11B, this embodimenthaving an alternative profile for the bioerodible material component107. This embodiment thus is initially formed as a curved nascent device200 (FIG. 29A), which is formed into a substantially flat implant device200′ (FIG. 29B), which upon implant and subsequent erosion of thebioerodible material, changes into a curved planar device 200″ (FIG.29C). The bioerodible material segments 107, as seen in FIGS. 29A and29B are wedge-shaped, in contrast to the spherical or cylindricalconfigurations depicted in FIGS. 10 and 11 respectively. Theconfiguration of the bioerodible segments may thus vary, a wedge-shapemerely being an example of such variation, and one that may provideadvantage in the device fabrication process.

FIGS. 12 and 13 show exemplary approaches by which an implantable devicecomprising resiliently deformable material and bioerodible material canchange shape by flattening a curve. FIG. 12A shows a curved proto-device200 that is comprised of deformable material in its preferred straightconfiguration, with sites 105 for the insertion of bioerodible materialpieces 107. FIG. 12B shows an implant-ready device 200′, with thebioerodible material 107 included in the sites 105 within the deformableportion 100 of the device. By such insertion, the device 200′ has beenforced to assume a curved configuration. FIG. 12C shows the device, nowin configuration 200″ following the erosion of the bioerodiblematerials, and by such erosion, the deformable portion has been freed toresume its preferred configuration, giving the device 200″ a straightshape.

FIG. 13A shows a planar proto-device 200 that is comprised ofresiliently deformable material in its preferred straight configuration,with linear sites 105 for the insertion of bioerodible material pieces107. FIG. 13B shows an implant-ready device 200′, with the bioerodiblematerial 107 included in the sites 105 within the deformable portion 100of the device. By such insertion, the device 200′ has been forced toassume a curved planar configuration. FIG. 13C shows the device, now inconfiguration 200″ following the erosion of the bioerodible materials,and by such erosion, the deformable portion has been freed to resume itsstraight configuration, giving the device 200″ a straight planar shape.

FIGS. 14A-14C show an embodiment of the shape-changing device thatexpands an existing curvature. FIG. 14A is of a proto-device 200 in apreferred configuration, in this case, a rod configured into a U- orhorseshoe-shape. On the outer aspect of the circumference bioerodiblematerial sites 105 (empty at this point) can be seen as narrow cuts. InFIG. 14B, the device 200′ has been forced into a narrower or V-shapedconfiguration, and the bioerodible material sites 105 have been filledwith biomaterial 107, such filling stabilizing the device in thenarrower configuration. FIG. 14C shows the device, now 200″, after thebioerodible material has eroded away, the device has radially expanded,the resiliently deformable material 100 having returned to its preferredshape. A device of this type has utility in expanding narrowedpharyngeal passageway, as described below and shown in FIGS. 21A-21C and22.

FIGS. 15A-15C show an example of the formation of an implantablerod-like device, or a linear portion of a device with two contrarycurves, forming a simple S-shape. FIG. 15A shows a planar proto-device200 that is comprised of resiliently deformable material in itspreferred S-shaped configuration, with linear sites 105 for theinsertion of bioerodible material pieces 107. FIG. 15B shows animplant-ready device 200′, with the bioerodible material 107 included inthe sites 105 within the deformable portion 100 of the device. By suchinsertion, the device 200′ has been forced to assume a straight planarconfiguration. FIG. 15C shows the device, now in configuration 200″following the erosion of the bioerodible materials, and by such erosion,the deformable portion has been freed to resume its preferredconfiguration, giving the device 200″ an S-shaped planar shape. FIGS.16A-16C depict a series analogous to that of FIGS. 15A-15C wherein thedevice, or portion of a device, is configured in a planar form ratherthan a rod, the plane extending perpendicularly in relation to the mainaxis.

Other embodiments of the invention can be understood to includevariations on this theme of alternating curves. It can be furtherunderstood, for example, that by varying the spacing of insertion sites105, and the size and depth of such insertion sites relative to thethickness of the resiliently deformable portion of the device, theangles formed at each vertex represented by an insertion site can becontrolled. Embodiments of a generally rod-like shape that have beendepicted have had the insertion sites 105 on either one side of the rod,or, in the case of the embodiment depicted in FIGS. 15A-15 c, theinsertion sites 105 occur on radially opposite sides of the rod. It thuscan be understood that other embodiments of the invention include thosewhere the insertion sites are not confined to a single radial positionon a rod, or on two opposite radial positions, but rather can windaround the rod, thereby creating embodiments that curve in a corkscrewmanner. Various embodiments may thus have a preferred configuration thatis either a straight or corkscrew like, and upon incorporation ofbioerodible material into insertion sites are contorted into acorkscrew-like or straight configuration, respectively, and upon erosionof the erodible material, once again assume the preferred configuration.

FIGS. 17A-17C show a rod-like shape-changing device or portion thereofthat changes shape after the erosion of peripherally-attachedbioerodible suture. The use of sutures is also illustrated by theembodiments depicted in FIGS. 30A-30D, as described above. In itsnascent form 200 (FIG. 17A) the present device is curved. In itsimplant-ready form 200′ (FIG. 17B) the device is straight, secured by asuture extending the length of the device and secured at either end. Inits post-implant, post-eroded form 200″ (FIG. 17C) the device is onceagain curved. Related embodiments may have more complex curves, and mayalso have a converse preferred: non-preferred shape scheme, where thedevice is curved upon implantation, and straightens during the course oferosion of the constraining bioerodible suture. Further, in otherembodiments encircling grooves may be in place, in varied form, and mayhave deepened portions at spaced intervals to provide security againstthe suture slipping within the groove. There may also be multiple suturesegments, and the segments may vary in thickness so their erosion timeswill vary, and allow release the device from its shape constraint over aprotracted time course.

FIGS. 18A-18E shows an example of a shape change where, once implanted,a two-dimensional substantially flat portion of a device can assume athree dimensional shape. In this particular embodiment, a bowl-shapedshape-changing device or portion thereof that assumes a disk-like shapeafter implantation. In its nascent form (FIG. 18A), the resilientlydeformable portion 100 of nascent device is bowl-shaped, and it hasslots 105 on its inner aspect for accommodating bioerodible material. Asthe device 200 is being formed (FIG. 18 b) into an implant ready device,it is flattened and combined with bioerodible material 107. In itsimplant-ready form 200′ (FIG. 18C), it has assumed a disk-like shape,with bioerodible material 107′ filling the accommodating slots. FIG. 18Dshows a cross-sectional portion of the disk-like form, with bioerodiblematerial-accommodating slots of various configurations (105 a-105 d) forconstraining the device as whole in a flat configuration. In itspost-implant, post-eroded form (FIG. 18E), the device or portion thereofhas returned to a bowl-like configuration. The embodiment depicted inFIG. 18 includes bioerodible material insertion sites or slots 105 thatare generally concentric, symmetric, and circumferentially complete.These characteristics can be varied in other embodiments. The insertionsites or slots, for example, may be asymmetrical, and may include arcsthat are circumferentially incomplete. By such variations, asymmetricalbowl-like or cup-like shapes of infinite variety can be formed, eitheras a preferred shape, or as a non-preferred shape.

FIGS. 31A-31D shows an example of a shape change where, once implanted,a three-dimensional device or portion thereof can change shape to becomea substantially flat device. In brief, FIGS. 31A-31D show a device thathas a three dimensionally curved configuration when at an implant readystage, which flattens upon erosion of bioerodible material. This deviceis, to some extent, functionally the complement of the device depictedin FIGS. 18A-18E, in that the previous (FIG. 18) device is in a flatconfiguration at implant, and assumes a three-dimensional bowl-likeconfiguration following implantation and bioerosion. FIG. 31A shows thedevice or components thereof 200 at a nascent stage where theresiliently deformable portion 100 is flat, and has leaf-cuts 112included to accommodate being curved. FIG. 31B shows the device 200′after being formed into a bowl-like shape, such shape stabilized by theincorporation of bioerodible material into slots on the outer surface ofthe curve, as shown in the cross-sectional view of FIG. 31C. FIG. 31Dshows the device 200′ in the flattened shape it returns to followingimplantation and erosion of the bioerodible material.

When the preferred shape (FIG. 31A) of this embodiment is being forcedinto a non-preferred shape (FIG. 31B), a surface compression thataccompanies such a shape change needs to be accommodated. This aspect ofthe formation of the device is thus more complex and not the converse ofthe stretching that occurs in the fabrication of so-called curve-formingdevices, as in the embodiments depicted in FIG. 18. Shape compression ishandled by an embodiment of the shape-changing method through the use ofcut-outs or leaf-cut 112 features as described further below.Bioerodible material 107 is seen in FIG. 31A prior to being conjoinedwith the resiliently deformable portion 100; it is seen also in FIG. 31Bwhen the resiliently deformable portion has now been formed into thenon-preferred shape of an implantable device 100′, and in thecross-sectional view (FIG. 31C).

Embodiments of a shape-changing device such as these (i.e., athree-dimensional curve to a two dimensional flat surface) may alsoinclude other advantageous features. Tissue-engaging features, asexemplified by holes, interstices, or pores 108 through the device,allow for tissue in-growth into the device after being implanted. Thesesites of in-growth, through or across the device embodiment, create anengagement between the device and the tissue, in the absence of tissuecould pull away from the device as the surface of the device advances ina pulling direction. These pores 108, in some embodiments, may be alsooccupied by bioerodible material when the device is in its implant readyform, and such holes may further contribute to the ability of the deviceto change shape by providing sites that can accommodate materialcompression during shape-changing.

The embodiments of shape-changing devices that are curved in theirimplant-ready form, and which flatten upon returning to a preferredshape may include leaf-cut features 112, which separate portions of thedevice in the form of cuts that penetrate from peripheral regions of thedevice toward the center of the device. The leaf-cut spaces of a nascentor proto-device in a flat form allow a three-dimensional curve to beimparted to the device or portion thereof without crimping, folding, orwrinkling that would otherwise occur. As the device as a whole is formedinto a three-dimensional or bowl-shaped curve, the leaf cuts cometogether in the third dimension. As the device in its implant ready formis eroded of shape-stabilizing bioerodible material, and flattens out,the leaf cuts emerge once again as separations between leaves of thedevice. Embodiments of devices such as these in FIG. 31 and in FIG. 18are shown in an in situ environment in FIGS. 32A, 32B, 33A, and 33B, asdescribed further below.

It may further be understood that by combining the variousabove-described approaches to changing shape geometrically infundamental ways, an immense variety of shape-changing forms may beembodied in implantable devices. By these approaches, an immense varietyof tissue reforming tasks may be created by such shape-changing devices.

D. Shape-Changing Devices In Situ Reshaping the Airway

The various shape-changing devices, described and depicted above ingeometric shape-changing terms, will now be described in terms ofvarious specific device embodiments and their airway-opening effectswhen implanted into various tissue sites that form the airway. FIGS.19-21 depict the use of an embodiment of an airway-opening device thatis implanted within the pharyngeal wall. This treatment method anddevice would be appropriate for a subject with an airway occlusion atthe level of the oropharynx, whereby posterior wall thickeningcontributes to the occlusion, particularly during sleep, as depicted indetail in FIGS. 2 and 3.

By way of a brief overview, FIGS. 19A and 19B provide sagittal views ofan airway with reference lines 20A and 20B, that are used to locate theplanes, respectively, for the coronal views of FIGS. 20A and 20B. FIG.19A depicts an airway with an occlusion 5 due to thickening andshortening of the posterior pharyngeal wall before treatment. FIG. 19Bdepicts with airway with an implanted shape-changing, linearly-expandingdevice (such as those, for example, depicted in FIGS. 8 and 9) that hasopened the obstructed region by expanding the pharyngeal wallssuperiorly and inferiorly, thus limiting or diminishing the amount ofthickening of the walls. In practice, one or more devices may beimplanted at circumferential intervals at the approximately samecephalad-caudal position along the airway, or at slightly varyingpositions. The embodiment of the device as shown in FIG. 19B is sizedand shaped to conform to a pharyngeal wall tissue site in a mannercompatible with normal physiological function of the site and thus thedimensions provided here are only an approximation for the purpose ofillustration, and are not meant to be limiting. The overall dimensionsmay vary according to the full extent that human subjects vary in theiranatomical dimensions. These considerations notwithstanding, a typicaldevice such as that depicted in FIG. 19B may have a length whenimplanted in the range of about 1 cm to about 5 cm, and after bioerosionand consequent lengthening, may have a length of about 2 cm to about 6cm.

FIGS. 20A and 20B provide coronal, downward-directed views of theairways depicted in FIGS. 19A and 19B. FIG. 20A shows obstructed by acompressed posterior pharyngeal wall; and FIG. 20B shows the resolutionof the compression by the implantation of a curve-expandingshape-changing device. FIG. 21 shows a schematic cutaway view of aportion of a pharyngeal wall that has been expanded by the implantationof a series of curve-expanding devices.

Now, in a more detailed description, FIG. 20A depicts the generaloropharyngeal site of occlusion 5 and the contribution of the thickenedand shortened posterior pharyngeal wall to the occlusion. An embodimentof a device 200′, depicted in detail in FIGS. 8A-8C is shown asimplanted in the pharyngeal wall in FIG. 20B. Particularly advantageousfeatures of this embodiment include the tissue-stabilizing end pieces205, on either end of the device, which provide a level of tractionagainst which the device can push, as the device lengthens as aconsequence of bioerosion, gradually taking the lengthened form ofdevice 200″. The end pieces 205 may generally take any of form that isappropriate for the implant site. Their function is to provide surfacearea for engagement between the tissue of the implant site and thedevice such that the device, as it lengthens, does not destructivelypush through tissue, but rather pushes against a tissue mass, linearlystretching that region of tissue, and over time, reforming and/ormaintaining it into a longer configuration. By lengthening the tissue ofthe pharyngeal wall or by maintaining it in a lengthened conformation,the thickness of the wall is consequently decreased, and thereby, inturn, expanding the opening of the adjacent or local portion of theairway.

FIGS. 20A-20B and 21 relate to a shape-changing device (such as, forexample, the embodiment depicted in FIG. 14) that is implanted into theposterior pharyngeal wall where it supports an expansion of thecircumference of the airway. FIGS. 19A and 19B serve as a orientingreferences for FIGS. 20A and 20B. The horizontal marking line throughthe sagittal view of an airway marks the level at which adownward-looking coronal view is taken; the cross hatched bilateralsections of the tongue 16 also serve as a useful reference. The softpalate 6 and posterior pharyngeal wall 22 define the circumferentialbounds of the airway at this level. Other local orienting featuresinclude the epiglottis 12, and the esophagus 34. FIGS. 19A and 20Adepict an airway that is narrowed because of a stenotic posteriorpharyngeal wall. FIGS. 19B and 20 b depict the same airway with a shapechanging device 200B implanted into the wall which has had the effect ofexpanding the radial curve circumscribed by the wall. In comparing theradius of the wall of FIG. 20A (preimplant) and 20B (post-implant, andpost erosion such that the device is in its preferred configuration), itcan be seen that the radius absent the implant is comparativelyV-shaped, and with the implant is comparatively U-shaped. The deviceimplanted into this site is an embodiment of the invention describedabove and depicted in FIGS. 14A-14C. The embodiment of the device asshown in FIGS. 20 and 21 is sized and shaped to conform to a pharyngealwall tissue site in a manner compatible with normal physiologicalfunction of the site and thus the dimensions provided here are only anapproximation for the purpose of illustration, and are not meant to belimiting. The overall dimensions may vary according to the full extentthat human subjects vary in their anatomical dimensions. If theembodiment is understood as to approximate a U-shape (U-shape in suchgeneral terms that it also includes a V-shape), typical dimensions,merely by way of example, could approximate a range of about 3 cm to 6cm across the U-shape, and a depth or height of about 1 cm to about 3cm.

FIG. 21 is cutaway, posteriorly-directed perspective view of therelevant portion of the pharyngeal wall into which three devices 200″ ofthis particular type have been implanted, and have, through bioerosion,expanded their curve toward the preferred shape of the device. Invarious embodiments of the method, one or more devices may be implanted.The embodiments depicted are V-shaped rods which, upon bioeroding andchanging into the preferred shape, take on a U-shaped configuration. Incross section, the depicted embodiments are substantially cylindrical,other embodiments may have other cross-sectional shapes, such as, merelyby way of example, flattened, belt-like shapes, or oval-shapes. Thesedevices are thus like the embodiment depicted in FIGS. 14A-14C, asdescribed above, wherein an implanted device has an existing curvature,and after implantation and subsequent erosion, the device changes shapeinto an expanded curvature, embracing an arc of greater radius. Someembodiments of the type shown in FIGS. 20 and 21 may also includelengthening features, as seen, for example in embodiments seen in FIG.6. Thus, while the device changes shape by expanding a curve,lengthening of arms of the device allows the device to embrace a largerarc, in this case, thereby more efficiently expanding the arc of theportion of the pharyngeal wall implant site.

FIGS. 22A-22C depict the insertion of an embodiment of an airway openingdevice 200A into the soft palate, the device of a type depicted in FIG.10 or 11. In various embodiments of the method of opening the airway,the device may be configured as rods or tubes, including one or morerods as in FIG. 10, or it may be a broadened, more planar structure, asin FIG. 11. FIG. 22A shows an embodiment of the method whereby a device200A is surgically inserted into the soft palate by extruding it from adeployment tube 210. The shape or configuration of the device 200Aembodiment is substantially straight (in the case of a rod-likeembodiment) or flat (in the case of a planar embodiment). FIG. 22B showsthe device 200A in situ after implantation. FIG. 22C shows the device,now having assumed the curved shape of device 200″, at some interval oftime after implantation. During the post-implant time interval thebioerodible portion of the device has eroded, the shape of the devicehas consequently changed, and, as can be seen, the shape of the softpalate 6 has accordingly reformed such that the airway 4 (occluded atlocation 5 in FIGS. 22A and 22B) is now open (FIG. 22C).

These sequences of shape-changing events, in reference both to thedevice and the soft palate, are depicted in FIG. 23A and FIG. 23B showsthe device 200′ at a very early stage after implantation into the softpalate 6. The device 200′ is substantially straight (or flat, in thecase of a planar embodiment) at this stage, and the bioerodible materialaccommodating sites 105 (bioerodible material not shown) within thedeformable material portion 100 are fully expanded, as they aremaximally filled with the bioerodible material. FIG. 23B shows a latestage following implantation, when the device has assumed a fully matureand curved configuration 200″ by virtue of the bioerodible sites 105 nowdepleted of erodible material and substantially closed, and the softpalate 6 now fully reformed, in accordance with the reforming of thedevice 200″ into its preferred and stable shape. The embodiment of thedevice as shown in FIGS. 22 and 23 is sized and shaped to conform to thesoft palate tissue site in a manner compatible with normal physiologicalfunction of the site. The overall dimensions may vary according to thefull extent that human subjects vary in their anatomical dimensions, andthus the dimensions provided here are only an approximation for thepurpose of illustration, and are not meant to be limiting. Theembodiment typically is implanted at a site immediately adjacent to thehard palate extending to about 1 cm posterior to it. In someembodiments, the device may be connected or affixed to the posterioredge of the hard palate, thus serving to effectively extend the lengthof the hard palate; further, the hard palate may be used as an anchortoward which the soft palate may be advanced. The device embodimenttypically is rod-shaped, is configured to reside in ananterior-posterior orientation, and has a range in length between about1 cm and about 2 cm, and has a diameter or thickness of a range of about1 mm to about 4 mm. In other embodiments, the device has a flattenedshape, and a width of about 5 mm to about 1.5 cm.

FIGS. 24A and 24B depict the use of an embodiment of an airway-openingdevice 200′ that shortens after implantation; it is implanted within thetongue, connected posteriorly to the hyoid bone 28 by a tissuestabilizing harness 205 and anteriorly by a tissue connector 207 into acentral site on the inner aspect of the mandible 24. The device shortensin a manner that is complementary to the mechanism depicted in somedetail in FIG. 8, which shows a lengthening mechanism. In thisshortening device embodiment 200′, resiliently deformable portions thathave a preferred configuration of being outwardly bowed are constrainedin a lengthened and linearized configuration of an encasing layer ofbioerodible material 107′. After implantation and subsequent bioerosion,the resiliently deformable portions assume their preferred, outwardlybowed configuration, thereby shortening the total length of the device,and pulling the hyoid bone 28 forward toward the jaw, and by suchpulling forward, creating a more open airway posterior to the tongue.This treatment would be appropriate for a subject with an airwayocclusion 5 at the level of the oropharynx, wherebyposteriorly-displaced tongue contributes to the airway occlusion,particularly during sleep, as depicted in detail in FIGS. 2 and 3.Embodiments of devices that shorten by erosion such as the devicesdepicted in FIGS. 24-26 may also be applied to the soft palate, wherethe hard palate may serve as an anchor, as mentioned above in thedescription of the embodiments depicted in FIGS. 22 and 23.

FIG. 24A shows the generally linear device shortly after implantation inits initial, full-length configuration. The initial length of the deviceis sized such that there is little if any force pulling the hyoidforward; this is advantageous for the procedure in that such minimalforce allows the implantation site to recover from the procedure,particularly at the points of anterior and posterior attachment, butalong the full length of the device as well. Such recovery typicallyincludes the development of a surrounding fibrotic capsule that createsa tissue adherence to the device, while protecting the immediatelysurrounding tissue from further damage. Over time, erosion of thebioerodible portion of the device occurs, and the device as a whole,begins to shorten, drawing the hyoid bone forward, and with it, the baseof the tongue, thereby facilitating the opening of the airway posteriorto the tongue. In the embodiment of the shortening device 200′ depictedin FIGS. 24A and 24B, the shortening mechanism includes the erosion of abioerodible capsule that constrains a lantern-like structure in astraight configuration, preventing it from flexing outward (see FIG.6C). As described above, and as depicted in the other exemplaryshortenable embodiments of FIGS. 6-8, any of these device embodimentscould be utilized for this purpose of drawing the hyoid bone forward.

The embodiment of the device as shown in FIGS. 24A and 24B is sized andshaped to conform to the tongue tissue site and the overall dimensionsof the jaw posterior to the mandible, is configured to reside in ananterior-posterior orientation, in a manner compatible with normalphysiological function of the site. The overall dimensions may varyaccording to the full extent that human subjects vary in theiranatomical dimensions, and thus the dimensions provided here are only anapproximation for the purpose of illustration, and are not meant to belimiting. The embodiment in its elongated state, as implanted (FIG.24A), may typically be in the range of about 5 cm to about 8 cm inlength, from the anterior end attached to the inner aspect of themandible, and the posterior aspect as attached or harnessed to the hyoidbone. In its contracted state, after bioerosion and shortening (FIG.24B), the device may be in the range of about 4 cm to about 7 cm inlength.

FIGS. 25A and 25B depict an embodiment that functions in a site andmanner that is similar to those of the embodiment depicted in FIGS. 24Aand 24B. The device embodiment 200″ differs in that rather than engagingthe hyoid as a proximal or posterior anchor, it internally engages thebase of the tongue 16. The posterior base 205 of the device is broad andflat, and oriented orthogonal to the main axis of the device in order toprovide engagement with a substantial amount of tongue tissue, thisbeing beneficially efficient in pulling the tongue forward. The devicebase 205 also may include holes, interstices, pores, or intercalationsites 108 (see in FIGS. 26A and 26B) through which tongue tissue maygrow, thereby further increasing the grip that the device has on thebase of the tongue. In some embodiments, the device may includetissue-engaging features such as hooks or barbs to more aggressivelyengage the tissue and the device together. The tissue-engaging base ofthe device 205 may generally be implanted in the central portion of thebase of the tongue, but this is not necessarily the only appropriateimplant site. It may be advantageous, in some embodiments of the methodof implanting this embodiment of the device, or other embodiments, toimplant the device off center, such that one side of the tongue ispreferentially pulled forward. Advantages of an off-center location mayderive from it simply being a more effective treatment to pull one sideforward, for example, there may be less force required, and it may bethe case that an off-center site is more forgiving in that a greaterrange of force allows effective pull forward without interfering withnormal tongue function.

FIGS. 26A and 26B provide a detailed view of a device embodiment thatmay be used as an alternative to the device shown in FIG. 25, thegeneral mechanism of decreasing length being that an embodimentdescribed above and shown earlier in FIGS. 6A-1 and 6A-2. Furtherdetails shown here include the tissue engaging pieces. The distal tissueengaging piece 205 includes a tissue connecter 111 mounted on a bracket110, the connecter being exemplified by a screw that can connect to themandible. The proximal or posterior tissue-engaging piece 205 includesholes or intercalation sites 108 for tissue in-growth. In other deviceembodiments, tissue interactive features such as the holes or pores 108may take other forms while serving the same function of engaging tissue,and stabilizing the implanted device. In some embodiments, for example,tissue interactive pores may not penetrate completely through a portionof a device, but may be a surface dimple. Further, while in theembodiment shown in FIG. 26 the hole or pore is on an ancillary portionof the device dedicated to tissue engagement, a tissue-engaging hole orpore may also be located on the resiliently deformable portion of thedevice, as seen in the embodiment shown in FIG. 31. Further, in someembodiments, particularly those where the tissue interactive pore is ona resiliently deformable portion of a device, such pore may also be asite which accommodates bioerodible material when the device is in itsimplant-ready form.

The embodiment of the device as shown in FIGS. 25A, 25B, 26A, and 26B issized and shaped to conform to the tongue tissue site and the overalldimensions of the jaw posterior to the mandible in a manner compatiblewith normal physiological function of the site. The overall dimensionsmay vary according to the full extent that human subjects vary in theiranatomical dimensions, and thus the dimensions provided here are only anapproximation for the purpose of illustration, and are not meant to belimiting. This embodiment is of similar dimension to the embodiment ofFIGS. 24A and 24B, although it can be understood that this embodimentmay have more variability in the implant site of the posterior end mayhave even more variability for not being associated with a specificlandmark such as the hyoid bone. The embodiment in its elongated state,as implanted (FIG. 25A), may typically be in the range of about 4 cm toabout 8 cm in length, from the anterior end attached to the inner aspectof the mandible, and the posterior aspect as embedded in the base of thetongue. In its contracted state, after bioerosion and shortening (FIG.25B), the device may be in the range of about 3 cm to about 7 cm inlength.

FIGS. 27A and 27B show another device embodiment that operates in amanner similar to the embodiments depicted in FIGS. 24-26, but with ashape-changing approach that although shortening in nature, is morecomplex than the approaches of the earlier embodiments. The deviceembodiment is of a type depicted in FIGS. 16A-16C; in its implant-ready(non-preferred) configuration the embodiment is a flat or substantiallyflat planar device. FIG. 27A shows the device 100′ in situ, implanted atits proximal end in the base of the tongue 16, and at its distal end byway of tissue connector 111 into the mandible 24. Over the course oferosion of the bioerodible material, as seen in FIG. 27 b, the shape ofthe plane of device 100 changes in a complex way; the posterior portionof the device bends upward, raising the base of the tongue and pullingit forward, and the anterior portion of the device bends downward,creating greater leverage for the upward lift of the base of the tongue.By the curving alone, irrespective of the direction of the curves, thedistance between the tongue and the jaw is shortened, drawing the tonguebase forward.

The embodiment of the device as shown in FIGS. 27A and 27B is sized andshaped to conform to the tongue tissue site and the overall dimensionsof the jaw posterior to the mandible in a manner compatible with normalphysiological function of the site. The overall dimensions may varyaccording to the full extent that human subjects vary in theiranatomical dimensions, and thus the dimensions provided here are only anapproximation for the purpose of illustration, and are not meant to belimiting. This embodiment is of similar dimension to the embodiment ofFIGS. 25 and 26, and may similarly include an element of variabilityassociated with the absence of a specific anatomical landmark such asthe hyoid bone at the posterior site of implantation. The embodiment inits elongated state, as implanted (FIG. 27A), may typically be in therange of about 4 cm to about 8 cm in length, from the anterior endattached to the inner aspect of the mandible, and the posterior aspectas embedded in the base of the tongue. In its contracted state, afterbioerosion, taking on an S-shaped curve (FIG. 27B), the device may be inthe range of about 4 cm to about 7 cm in anterior-posterior end-pointlength.

FIGS. 28A and 28B depict yet another embodiment of a device 200 thatdraws the tongue forward. This particular embodiment screws into thecentral inner aspect of the mandible with tissue connector 111 mountedon tissue stabilizing base 205, as do the embodiments depicted in FIGS.25-27, and is anchored in tissue in the base of the tongue. Theembodiment includes two parallel strands that shorten as a consequenceof the erosion of bioerodible material, in the manner shown in detail inFIGS. 7A-7E. FIG. 28A shows the strands in their preferred configurationas they would be in their proto-device form, prior to the incorporationof bioerodible length-stabilizing portions; FIG. 28B shows the device inits implant ready form. The posterior ends of both strands are attachedto a connecting piece, a tissue grasping end piece 205, with tissueintercalating sites 207, similar to those of FIGS. 26A and 265.

The embodiment of the device as shown in FIGS. 28A and 28B is sized andshaped to conform to the tongue tissue site and the overall dimensionsof the jaw posterior to the mandible in a manner compatible with normalphysiological function of the site. The overall dimensions may varyaccording to the full extent that human subjects vary in theiranatomical dimensions, and thus the dimensions provided here are only anapproximation for the purpose of illustration, and are not meant to belimiting. This embodiment is of similar dimension to the precedingembodiments designed for implantation in tongue tissue. The embodimentin its elongated state, as implanted (FIG. 28A), may typically be in therange of about 4 cm to about 8 cm in length, from the anterior endattached to the inner aspect of the mandible, and the posterior aspectas embedded in the base of the tongue. In its contracted state, afterbioerosion and thereby shortening (FIG. 28B), the device may be in therange of about 4 cm to about 7 cm in anterior-posterior end-pointlength. The bioerodible segments 107 that occupy sites 105, as seen inFIG. 28A may be of any suitable length, but as illustrated in thisexemplary manner, are depicted as being about 1 cm in length. The sites105 into which the bioerodible segments are fitted are stretched toaccommodate the bioerodible segments, but their preferred length, andthe length to which they return upon the erosion and disappearance ofthe segments 107 may be about 0.7 cm.

FIGS. 32 and 33 schematically depict devices of the type described aboveand depicted, respectively, in detail in FIG. 18 (i.e., an implantableflat disk assuming a bowl-shape after bioerosion) and FIG. 31 (i.e., animplantable bowl-shape assuming a flat shape after bioerosion), asimplanted in the base of the tongue. FIGS. 32 and 33 all provide viewslooking down on a tongue 16, with the tongue base at the right. FIG. 32Adepicts an implanted device 100′ in the form of a flattened disk,circular or ovoid (an embodiment like that of FIG. 18); the device isshown as if the tongue were transparent, and is oriented perpendicularlyto the main axis of the tongue, with the surfaces of the device facingtoward the back and front of the tongue. The device configuration neednot be circular or ovoid; it could be of any shape that conforms to theimplant site in the base of the tongue, such as being substantiallyrectangular. In the simplest perspective, the device may be understoodas planar, whether or not a bowl-form aspect is also present, and thegenerally planar structure is oriented orthogonally to the mainposter-anterior axis of the tongue. FIG. 32B shows the device afterbioerosion that has changed the shape of the device such that theanterior, forward-facing surface of the device having assumed abowl-shape, the convex surface facing anteriorly, and the concavesurface facing posteriorly, toward the airway. With the forward movementof the emerging concavity, the device pulls the central portion of thebase of the tongue forward, thereby creating a more open airway.

FIG. 33A depicts an implanted device 100′ in the form of a bowl-shapeddisk, circular or ovoid (an embodiment like that of FIG. 31); the deviceis shown as if the tongue were transparent, and is orientedperpendicularly to the main axis of the tongue, with the surfaces of thedevice facing toward the back and front of the tongue. The device isoriented such that as implanted, the concave surface is facinganteriorly, and the convex surface is facing posteriorly, toward theairway. FIG. 32B shows the device after bioerosion that has changed theshape of the device it has become substantially flat. As the device hasflattened, it has pushed tissue anterior to it forward, and it has alsopulled tissue posterior to it forward, thereby creating a more openairway.

The embodiment of the devices as shown in FIGS. 32 and 33 are sized andshaped to conform to the tongue tissue site in a manner compatible withnormal physiological function of the tongue. The overall dimensions mayvary according to the full extent that human subjects vary in theiranatomical dimensions, and thus the dimensions provided here are only anapproximation for the purpose of illustration, and are not meant to belimiting. The device is configured to fit into a site in the base of thetongue, orthogonal to the main axis of the tongue. As noted above, thedevice may be generally circular in two-dimensional shape (includingvariations of a circular shape, such as an ovoid shape), and in someembodiments, the generally circular shape may be compounded with a thirddimensional bowl-like shape. Further, the shape of the embodimentdepicted in FIG. 31 may be embellished with leaf cuts 112, which cangive a clover-like appearance to the generally circular shape. Theseshape variations and dimensional variables being understood, typical,though not-limiting dimensions of the device may include a diameter thatvaries in the range of 0.8 cm to 2.5 cm.

Terms and Conventions

Unless defined otherwise, all technical terms used herein have the samemeanings as commonly understood by one of ordinary skill in the art towhich this invention belongs. Specific methods, devices, and materialsare described in this application, but any methods and materials similaror equivalent to those described herein can be used in the practice ofthe present invention. While embodiments of the inventive device andmethod have been described in some detail and by way of exemplaryillustrations, such illustration is for purposes of clarity ofunderstanding only, and is not intended to be limiting.

Various terms have been used in the description to convey anunderstanding of the invention; it will be understood that the meaningof these various terms extends to common linguistic or grammaticalvariations or forms thereof. It will also be understood that whenterminology referring to devices or equipment has used trade names,brand names, or common names, that these names are provided ascontemporary examples, and the invention is not limited by such literalscope. Terminology that is introduced at a later date that may bereasonably understood as a derivative of a contemporary term ordesignating of a subset of objects embraced by a contemporary term willbe understood as having been described by the now contemporaryterminology.

While some theoretical considerations have been advanced in furtheranceof providing an understanding of the invention the claims to theinvention are not bound by such theory. Described herein are ways thatembodiments of the invention may engage the anatomy and physiology ofthe airway, generally by opening the airway during sleep; thetheoretical consideration being that by such opening of the airway, theimplanted device embodiments alleviate the occurrence of apneic events.Moreover, any one or more features of any embodiment of the inventioncan be combined with any one or more other features of any otherembodiment of the invention, without departing from the scope of theinvention. Further, it should be understood that while these inventivemethods and devices have been described as providing therapeutic benefitto the airway by way of intervention in tissue lining the airway, suchdevices and embodiments may have therapeutic application in other siteswithin the body, particularly luminal sites. Still further, it should beunderstood that the invention is not limited to the embodiments thathave been set forth for purposes of exemplification, but is to bedefined only by a fair reading of claims that are appended to the patentapplication, including the full range of equivalency to which eachelement thereof is entitled.

What is claimed is:
 1. A device for alleviating tissue obstruction of anairway in a human subject comprising: a first end; a second end; anelastomeric medial portion extending between the first and second ends,the medial portion having a linear configuration, a curvilinearconfiguration, and a site adapted to receive a plurality of bioerodiblesegments, wherein the device is configured to transition from thecurvilinear configuration toward the linear configuration upon erosionof the bioerodible segments, the device being sized and shaped to beimplanted in an airway-forming tissue site in a manner compatible withnormal physiological function of the site.
 2. The device of claim 1,wherein the curvilinear configuration comprises varying degrees ofcurvature along the medial portion.
 3. The device of claim 1, whereinthe curvilinear configuration comprises an s-shaped curve.
 4. The deviceof claim 1, wherein the curvilinear configuration comprises a concaveportion and a convex portion.
 5. The device of claim 1, wherein thebioerodible segments comprise a plurality of discrete bioerodible piecesadapted to engage the said site to maintain the device in thecurvilinear configuration.
 6. The device of claim 1, wherein the linearconfiguration comprises a substantially straight planar form.
 7. Thedevice of claim 1, wherein the curvilinear configuration comprises anexpanded state for said site, wherein the bioerodible segments fill thesite to maintain the curvilinear configuration.
 8. The device of claim1, wherein the device comprises a tissue in-growth portion.
 9. Thedevice of claim 1, wherein the device has a diameter between about 1 mmto about 4 mm.
 10. The device of claim 1, wherein the curvilinearconfiguration has a first length between about 4 cm to about 8 cm andthe linear configuration has second length between about 4 cm to about 7cm.
 11. The device of claim 1, wherein the device has a length betweenabout 1 cm and 2 cm.